Telfer won 22 caps for Scotland between his debut against France in 1964 and 1970, captaining his country on most of his appearances.

Telfer went on two British and Irish Lions tours, the first to New Zealand in 1966, then to South Africa two years later. He also toured New Zealand with Scotland in 1967.

Following his retirement from playing Telfer went on to coach the 1984 Grand Slam winning Scotland side and also coached the the victorious 1997 Lions with countryman Ian McGeechan who scored a famous series victory of the Springboks. Telfer's hard-man attitude and inspirational team-talks were a feature of the tour and his forwards were well-drilled and aggressive in the face of the World Champion Springboks.